Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B15/00—Preparation of other cellulose derivatives or modified cellulose, e.g. complexes
  • C08B15/05—Derivatives containing elements other than carbon, hydrogen, oxygen, halogens or sulfur
  • C08B15/06—Derivatives containing elements other than carbon, hydrogen, oxygen, halogens or sulfur containing nitrogen, e.g. carbamates

Definitions

• the present invention relates to a procedure for manufacturing cellulose carbamate by reacting isocyanic acid and cellulose at elevated temperature.
• Both Finnish Pat. Nos. 61033 and 62318 disclose a procedure for manufacturing an alkali-soluble cellulose derivative from cellulose and urea.
• the procedure is based on the fact that when urea is heated to its melting point or to a higher temperature it begins to decompose to isocyanic acid and ammonia.
• the isocyanic acid reacts with cellulose, producing an alkali-soluble cellulose derivative, called cellulose carbamate.
• the reaction may be written as follows: ##STR1##
• the cellulose compound thus produced, namely cellulose carbamate may be dried after washing and stored even for prolonged periods, or it may be dissolved, for instance for fiber production, in an aqueous alkali solution.
• Cellulose carbamate fibers or films may be manufactured from such solution by spinning or by extruding, in the same manner as in the viscose manufacturing process.
• the stability of cellulose carbamate and the feasibility of its transport in dry state afford a great advantage compared with cellulose xanthate in the viscose method, since the latter cannot be stored or transported, neither in dry nor in solution form.
• urea decomposes under the effect of heat to isocyanic acid and ammonia
• certain additional side reactions occur.
• One such side reaction is the reaction of isocyanic acid with urea, whereby biuret is produced.
• This biuret is still present, after the carbamate reaction, in the carbamate that has been produced and has to be removed, e.g. by washing.
• the present invention is directed to a new method for manufacturing cellulose carbamate by reacting isocyanic acid and cellulose at elevated temperature, wherein cellulose with biuret, or a mixture of biuret and urea, admixed thereto or absorbed therein, is heated at a temperature over 170° C. for suitable time to produce sufficient iscyanic acid for accomplishing the reaction between cellulose and isocyanic acid, thus forming the cellulose carbamate.
• urea is in fact not indispensable, and biuret may be used instead.
• Biuret which is an additional product of urea and isocyanic acid, is decomposed to urea and isocyanic acid again at temperatures over 170° C. Urea decomposes further to isocyanic acid and ammonia.
• urea biuret or a mixture of biuret and urea if temperatures are used which are so high that decomposition of urea will begin.
• biuret By using biuret, a very flexible process is attained. Since, in manufacturing cellulose carbamate, biuret is produced as an additional product of isocyanic acid and urea, in accordance with the present invention, biuret may be appropriately used as a reagent to be added to the cellulose and may be properly recycled straight to the beginning of the method, for processing a new batch of cellulose.
• the nitrogen consumed in the process may be made up either by adding urea or by adding biuret.
• a working temperature range in the procedure of the present invention is from about 170° to 250° C., the temperature most preferably being about 220° C. Temperatures over 250° C. should be avoided, because the risk of side reactions then increases.
• the required biuret quantity in the procedure of the invention is 3-50% by weight of the cellulose quantity.
• the amount of isocyanic acid produced on heating may be too low, while using greater amounts of biuret is neither economical nor even necessary in view of the reaction.
• urea In addition to biuret, it is also possible to use urea, if desired.
• the amount of urea in the procedure of the invention may be from 0 to 95% by weight of the weight of cellulose and biuret.
• the biuret or mixture of biuret and urea may be composed of biuret or a mixture of biuret and urea that did not react and was washed out of the product after the carbamate reaction. It should be noted that the product contains marked amounts of biuret and urea, after the carbamate reaction.
• the biuret may be added to the cellulose as raw material, for instance in an appropriate solvent.
• a suitable solvent in association with biuret and urea is ammonia, which is preferably, though not necessarily, in liquid form. In that case, either a low temperature is used or dissolving is accomplished under pressure.
• the requisite quantity of biuret, or mixture of biuret and urea is dissolved in ammonia, and the cellulose is impregnated with the solution, whereafter the ammonia is removed for instance by evaporating.
• the cellulose may be in the form of loose chains or of a web.
• the required absorbing time varies, usually from a few seconds to several hours and it is not critical, provided that sufficient biuret is applied to the cellulose fibers.
• the cellulose may be conducted through the ammonia treatment, for instance, by being carried on wires.
• the cellulose used in manufacturing carbamate may be pretreated for lowering the degree of polymerization. Adjustment of the degree of polymerization may be effected, e.g. by alkali treatment or by irradiation.
• the heating of the cellulose and the biuret is carried out, for instance, in a volume like a heat chamber, or by conducting a cellulose web or mat containing biuret through a liquid bath at the required temperature.
• Cellulose in the form of the web may be conducted, supported by wires or the equivalent.
• a liquid is chosen which does not dissolve biuret or urea. The lower the temperature at which the liquid boils, the easier is its removal on concluding the reaction, for instance by evaporating.
• Suitable liquids are, for instance, aromatic or aliphatic hydrocarbons with comparatively low boiling points.
• the end product is washed once or several times, for instance with water-free methanol, and dried.
• the end product is also preferably washed with liquid ammonia, whereby an advantage is gained in that the ammonia mixture containing biuret and urea, used as washing liquid, can be directly reused.
• the cellulose used as starting material in the procedure of the invention may be wood cellulose or cotton, or other natural or synthetic fibers containing cellulose.
• the cellulose may be present as such or in a chemically treated form, for instance bleached, as cellulose hydrate, as alkali cellulose, or in a form treated in another way, for instance with acids.
• Bleached spruce sulphite cellulose in sheet form (700 g/m 2 ), was treated with the aid of irradiation in order to adjust its DP (degree of polymerization) to be 420.
• the irradiation was carried out as electron irradiation (400 keV).
• the sheets were impregnated for five minutes at -35° C. with liquid ammonia in which 5% biuret had been dissolved.
• the ammonia was allowed to evaporate at room temperature for a few hours, whereby the quantity of biuret left in the cellulose was 13% by weight of the cellulose weight.
• Biuret-impregnated sheets were heated, by pressing between hot plates at 220° C. and at 240° C. The heating time was 5 min. at the lower temperature and 2 min. at the higher temperature. The sheets were washed three times with water and once with methanol. The carbamate was established by spectroanalytical (IR, 13 C NMR) and chemical methods. A solution was prepared of the sheets in a 10% NaOH solution at -5° C. so that the carbamate content of the solution was 5.7% by weight. From the solution, the clogging number and the viscosity were measured. The results are set forth in Table I below:
• Example 1 was repeated with the impregnating solution containing 10% biuret, whereby 22% by weight biuret was retained in the cellulose after removing the ammonia.
• the results are set forth in Table II.
• the ammonia contained 6% biuret and 4% urea.
• the ammonia was allowed to evaporate at room temperature, whereafter the sheets contained biuret and urea totalling 22%.
• the clogging number of the solution was found by measurement to be 1500 and the viscosity, 120 s.
• the nitrogen content of the carbamate was 1.5%.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Biochemistry (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Applications Claiming Priority (2)

Publications (1)

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Cited By (10)

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Citations (5)

• 1984
  • 1984-03-12 FI FI840999A patent/FI67562C/fi not_active IP Right Cessation
• 1985
  • 1985-03-01 ZA ZA851594A patent/ZA851594B/xx unknown
  • 1985-03-05 AT AT0065285A patent/AT390259B/de not_active IP Right Cessation
  • 1985-03-11 DE DE19853508611 patent/DE3508611A1/de active Granted
  • 1985-03-11 IN IN178/CAL/85A patent/IN161858B/en unknown
  • 1985-03-11 IT IT19846/85A patent/IT1200409B/it active
  • 1985-03-11 BR BR8501074A patent/BR8501074A/pt not_active IP Right Cessation
  • 1985-03-11 SE SE8501188A patent/SE459177B/sv not_active IP Right Cessation
  • 1985-03-11 RO RO117935A patent/RO91350B/ro unknown
  • 1985-03-11 DD DD85274010A patent/DD234019A5/de not_active IP Right Cessation
  • 1985-03-11 CS CS851697A patent/CS254982B2/cs unknown
  • 1985-03-11 NO NO850955A patent/NO161441C/no unknown
  • 1985-03-12 GB GB08506375A patent/GB2155479B/en not_active Expired
  • 1985-03-12 US US06/710,689 patent/US4567255A/en not_active Expired - Fee Related
  • 1985-03-12 JP JP60049197A patent/JPS60210601A/ja active Granted
  • 1985-03-12 CA CA000476303A patent/CA1238042A/en not_active Expired
  • 1985-03-12 FR FR8503615A patent/FR2560882B1/fr not_active Expired

Patent Citations (5)

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